Flutter Auth Flow Setup

I’m kicking off a new Flutter app and need a solid, production-ready authentication flow for this first milestone. My priority is straightforward email-and-password sign-up, sign-in, and password-reset screens fully wired to a secure backend (Firebase Auth or any equally reliable Flutter-friendly service—feel free to suggest the best fit). Two-factor authentication isn’t required yet, but please structure the code so I can add it later without rewiring the whole project.

Deliverables I need from you:
• Cleanly coded Flutter pages for register, log in, forgot-password, and logged-in landing state
• Integration with the chosen auth provider, complete with server-side validation and secure token handling
• Basic form validation and helpful in-app error messages
• Brief setup notes so I can run the flow locally and hook it into future features

If you have reusable modules for Google, Facebook, or Twitter login, mention that in your bid; I might extend the scope after this phase. I’m looking for concise, well-commented Dart code that follows Flutter best practices and is ready to drop into my existing repo.